Advances in Aeration Control. MWEA Fall Process Seminar November 6, :15 AM East Lansing, MI Thomas E. Jenkins President JenTech Inc.

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1 Advances In Aeration Control MWEA Fall Process Seminar November 6, :15 AM East Lansing, MI Thomas E. Jenkins President JenTech Inc. JenTech Inc N. Elm Tree Road Milwaukee, WI Advances in Aeration Control Importance of Aeration Control Advances in Aerators Diffused Mechanical New Blower Technologies Turbo Screw Blowers Advances in VFDs Improved Instrumentation & Control Strategies DO Control Techniques Feedforward Control 2 2 1

2 Factors Driving Advances in Aeration Control More Demanding Permit Requirements More Complicated Processes Higher Energy Costs Increased Global Technology Transfer Improved Instrumentation Hardware 3 3 Improved Control Means More Stable Processes Process Performance Comes First! Adapting Automatically to Upsets and Changes Can Improve Performance Control Strategies Must Integrate Process Equipment Characteristics Most Municipal WWTPs Operate at 1/3 of Design Capacity 4 CONSIDER TAKING TANKS OUT OF SERVICE 4 2

Energy Cost Rates vary with: Time of Day On peak, Off Peak Day of Week Size of Costumer Demand (kw) and Consumption (kwh)

3 Energy Is A significant Concern, and Can Be Used To Justify Systems Aeration is the Most Significant Energy Use in a WWTP 55% 34% Pumping and Other HVAC 11% Aeration 5 Most Utilities Offer $ Incentives for Reducing Energy Use 5 Energy Consumpon Energy Cost Rates vary with: Time of Day On peak, Off Peak Day of Week Size of Costumer Demand (kw) and Consumption (kwh) The First Goal of an ECM (Energy Conservation Measure) is to Reduce Cost While Maintaining or Improving Process Performance 6 6 3

4 Mechanical Aerators Variable Speed or On/Off Mechanical Aerators gth Power bhp/ft. rotor leng OTR lb/hr/ft rotor length 10 5 SOTR rpm rpm SAE lb/hp hr SAE rpm 7 Diffused Aeration Coarse Bubble Changing to Fine Pore Diffusers Should Always Be Examined! 8 8 4

9 New Aeration Technologies: Mixing and Aeration Combined Actually Re invention of Older Technology Allows Separate Control of Oxygen Transfer

Submergence Deeper is Better Also Requires Higher Blower Power Proportional to Air Flow per Diffuser Flux Rate (1 to 10 SCFM/ft 2 Typical)

5 9 New Aeration Technologies: Mixing and Aeration Combined Actually Re invention of Older Technology Allows Separate Control of Oxygen Transfer and Mixing Energy New Diffuser Geometries and Materials Fouling Resistance Improved OTE 9 Diffused Aeration Energy 10 Proportional to Submergence Deeper is Better Also Requires Higher Blower Power Proportional to Air Flow per Diffuser Flux Rate (1 to 10 SCFM/ft 2 Typical) Lower is better Proportional lto Actual At ldo Concentration ti Lower is Better DO Control is Significant Most Plants Are Too Conservative In DO Setpoint 10 5

6 Diffused Aeration Blower Power Ratio (Compared to 2.0 ppm DO) 4.50 Nominal Power Multiplie er Q Q actual 2.0 C C * * C actual Actual DO Concentration, ppm Based on 500' ASL, 55 F, 9.9 ppm C sat Excess DO means significantly more aeration power. 11 Impact on Control Systems Lower Air Flow Rates Reduce Valve Sizes Re Scale or Replace Flow Transmitters Mixing Limits Impact on Blowers Turndown May Become an Issue Verify Pressure Capacity (More Submergence) DO Control Maximizes Savings Opportunity Over Aeration More Common

7 Aeration Blowers and Energy Efficiency Varies with Blower Type Range is 60% to 80% Blower Considerations Efficiency Across Actual Load Spectrum Control Constant Pressure or Flow Based Control and Protection Should Be Integrated Turndown Often More Important Than Efficiency Turndown Limits Must Be Included In Control Strategy

8 Example Turbo Blower Characteristics System Curve Example Screw Blower Characteristics kw SCFM/k Typical Screw Blower Performance at Constant Speed 55 F T i 14.4 p i psig Discharge 68.0% 67.0% 66.0% 65.0% 64.0% 63.0% 62.0% 61.0% 60.0% fficiency Adiabatic Ef SCFM/kW Wire to Air Efficiency

9 Blower Control Considerations Blower Control Usually Included In Packages Screw Blowers Typically More Turndown Control Simpler Turbo Blowers Often More Efficient and Lower Cost (CHANGING) Turndown Limits Must Be Included din Control Strategy Surge Is a Concern VFD Applications Have Changed VFDs Are More Reliable And Less Costly Many Utilities Offer Automatic VFD Incentives Can Be Applied to ALL Types of Blowers Proper Selection and Engineering is Required 18 Medium Voltage (> 600 Volts) Now Cost Effective Increased Competition, Lower Prices Typically Greater Than 750 hp 18 9

10 Payback on Medium Voltage Drives Can Be Good Capital + Cu umulative Energy $14,000,000 $12,000,000 $10,000,000 $8,000,000 $6,000,000 $4,000,000 $2,000,000 $- Cumulative Operating Cost Years of Operation Exisitng Guide Vane Control New 2000 hp motor, 2000 hp VFD DO Control Can Be Very Cost Effective Will Save 25% Or More Compared to Manual Matches Air Supply To Demand Usually Improves Process Stability DO Is An Indirect Indicator of Process Performance Low Capital Cost May Make Payback Shorter Than Other Changes Control Complexity Should Be Matched to System Total oa Blower Air Flow Only Individual Basin Flow Control Separate Grid DO and Flow Control Within Basins New Strategies Improve Efficiency Most Open Valve Direct Flow Control Eliminates Pressure Control 20 10

11 Most Open Valve Control MOST Open Valve (MOV) Control is NOT Necessary for DO Control or Blower Control Technique for Minimizing System Pressure by Keeping at Least One Basin Valve at Max Position at All Times Older Systems Work By Adjusting Pressure Setpoint Newer Strategies Work Directly With Flow Control Pressure Control If Constant Pressure Is Maintained Changes in One Valve Won t Affect Other Basin s Air Flows If Pressure Setpoint is Too High Power Is Wasted 10.0 Typical Centrifugal Blower & System Curves 9.0 re, psig Pressu Pressure Setpoint 6.0 Wasted Power Flow, SCFM

Direct Flow Control Is Simpler and More Stable Typically Reduces Blower Power 5% to 10% 23 23 New Analytic

Nutrient Analysis Instruments Chiefly for Nutrients Nitrification/Denitrification Many Still Maintenance Intensive

12 Direct Flow Control Is Simpler and More Stable Typically Reduces Blower Power 5% to 10% New Analytic Instruments for Control Optical DO Probes Replacing Membrane Types Multi Channel and Remote Transmitters New Nutrient Analysis Instruments Chiefly for Nutrients Nitrification/Denitrification Many Still Maintenance Intensive Most Ammonia Control Strategies Used In Conjunction with DO Control New Feedforward Controls Based on Measuring Process Demand

Offgas Based Feed Forward Control Determines Air Demand By

Simple Payback To Calculate Cost Effectiveness Process

Use Present Worth for Longer Time Periods Implementation for

13 Offgas Based Feed Forward Control Determines Air Demand By Measuring OUR and OTE More Stable and Precise Use Simple Payback To Calculate Cost Effectiveness Process Requirements Come First! Use Present Worth for Longer Time Periods Implementation for Energy Conservation Should Be Justified By Best Payback Payback, years EquipmentCost AnnualSavings

14 Aeration and Energy Over Life of Equipment: Energy Cost is more Significant than Equipment, Installation, or Maintenance Costs Questions? html

Aeration System Improvements with a 5-Year Payback. Scott Phipps

Aeration System Improvements with a 5-Year Payback Scott Phipps Wastewater Treatment Aeration Timeline 1970 s Major infrastructure investment Quick and cheap solutions Coarse bubble diffusers & PD/MS blowers